1. Field of the Invention
Aspects of the present invention relate to an image forming apparatus that performs shading correction to prevent quality deterioration of image data and a control method thereof.
2. Description of the Related Art
Generally, an image forming apparatus (such as a digital multifunction machine, a copying machine, a scanner, and a facsimile) includes a scanning device to scan image data of a document. The scanning device emits light from a light source to the document and photoelectrically converts the light reflected from the document through an image sensor to generate an image signal.
During the generation of the image signal of the document, the image signal may be distorted due to a deviation of the light source or a non-uniformity of light quantity. The distortion of the image signal is known as a shading phenomenon.
A general image forming apparatus performs shading correction to compensate for the distortion of the image signal. The shading correction includes an image processing operation that compares image data of a document with reference data to decide a white pixel value or a black pixel value, and corrects an abnormal pixel with values of surrounding pixels. The reference data is image data read from a white reference plane before the image of the document is acquired.
According to the conventional art, the shading correction is performed on the abnormal pixel irrespective of whether the abnormal pixel is generated due to contamination of the white reference plane or contamination of a scan glass or an optical path.
The abnormal pixel generated due to the contamination of the scan glass or the optical path is repetitively generated whenever the document is scanned. For this reason, shading correction is performed to prevent quality deterioration.
However, when reference data is acquired from a white reference plane of a white bar disposed above the scan glass, the quality of the image data of the document may not be deteriorated, because the scanning process is carried out while the document is located between the white bar and the scan glass. Consequently, when the shading correction is performed within the range in which the abnormal pixel is generated, the quality of the image data of the document deteriorates.